Packages with Si-substrate-free interposer and method forming same

ABSTRACT

A method includes forming a plurality of dielectric layers, forming a plurality of redistribution lines in the plurality of dielectric layers, forming stacked vias in the plurality of dielectric layers with the stacked vias forming a continuous electrical connection penetrating through the plurality of dielectric layers, forming a dielectric layer over the stacked vias and the plurality of dielectric layers, forming a plurality of bond pads in the dielectric layer, and bonding a device die to the dielectric layer and a first portion of the plurality of bond pads through hybrid bonding.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/538,179 filed on Aug. 12, 2019, which is a continuation of U.S.patent application Ser. No. 16/204,628, filed on Nov. 29, 2018, now U.S.Pat. No. 10,381,298, issued on Aug. 13, 2019, which is divisional ofU.S. patent application Ser. No. 15/707,237, entitled “Packages withSi-Substrate-Free Interposer and Method Forming Same,” filed on Sep. 18,2017, now U.S. Pat. No. 10,290,571 issued May 14, 2019, whichapplications are incorporated herein by reference.

BACKGROUND

The packages of integrated circuits are becoming increasing complex,with more device dies packaged in the same package to achieve morefunctions. For example, a package may include a plurality of device diessuch as processors and memory cubes bonded to a same interposer. Theinterposer may be formed based on a semiconductor substrate, withthrough-silicon vias formed in the semiconductor substrate tointerconnect the features formed on the opposite sides of theinterposer. A molding compound encapsulates the device dies therein. Thepackage including the interposer and the device dies are further bondedto a package substrate. In addition, surface mount devices may also bebonded to the substrate. A heat spreader may be attached to the topsurfaces of the device dies in order to dissipate the heat generated inthe device dies. The heat spreader may have a skirt portion fixed ontothe package substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 27A illustrate the cross-sectional views of intermediatestages in the formation of silicon-substrate-free (Si-less) packages inaccordance with some embodiments.

FIGS. 27B, 27C, 27D, and 27E illustrate the cross-sectional views ofSi-less packages in accordance with some embodiments.

FIGS. 28 through 32 illustrate the cross-sectional views of intermediatestages in the formation of Si-less packages in accordance with someembodiments.

FIGS. 33 through 35 illustrate the cross-sectional views of intermediatestages in the formation of Si-less packages in accordance with someembodiments.

FIGS. 36 and 37 illustrate the cross-sectional views of packagesembedding Si-less packages in accordance with some embodiments.

FIG. 38 illustrate some top views of self-align metal pads used inSi-less packages in accordance with some embodiments.

FIG. 39 illustrates a process flow for forming a package in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package formed based on a silicon-substrate-free (Si-less) interposerand the method of forming the same are provided in accordance withvarious exemplary embodiments. The intermediate stages of forming thepackage are illustrated in accordance with some embodiments. Somevariations of some embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIGS. 1 through 27A illustrate the cross-sectional views of intermediatestages in the formation of a package in accordance with some embodimentsof the present disclosure. The steps shown in FIGS. 1 through 27A arealso reflected schematically in the process flow 300 shown in FIG. 39.

FIG. 1 illustrates carrier 20 and release layer 22 formed on carrier 20.Carrier 20 may be a glass carrier, a silicon wafer, an organic carrier,or the like. Carrier 20 may have a round top-view shape, and may have asize of a common silicon wafer. For example, carrier 20 may have an8-inch diameter, a 12-inch diameter, or the like. Release layer 22 maybe formed of a Light To Heat Conversion (LTHC) material, which may beremoved along with carrier 20 from the overlying structures that will beformed in subsequent steps. In accordance with some embodiments of thepresent disclosure, release layer 22 is formed of an epoxy-basedthermal-release material. Release layer 22 may be coated onto carrier20. The top surface of release layer 22 is leveled and has a high degreeof co-planarity. In accordance with alternative embodiments, instead ofusing carrier 20 and release layer 22, a silicon wafer, which is markedas 23. Dielectric layer 24 is formed on release layer 22. In accordancewith some embodiments of the present disclosure, dielectric layer 24 isformed of a non-polymer (inorganic material), which may be siliconoxide, silicon nitride, silicon oxynitride, or the like. When thesilicon wafer is used, layer 24 may be formed directly on silicon wafer23.

Redistribution Lines (RDLs) 26 are formed over dielectric layer 24. Theformation of RDLs 26 may include forming a seed layer (not shown) overdielectric layer 24, forming a patterned mask (not shown) such as aphoto resist over the seed layer, and then performing a metal plating onthe exposed seed layer. The patterned mask and the portions of the seedlayer covered by the patterned mask are then removed, leaving RDLs 26 asin FIG. 1. In accordance with some embodiments of the presentdisclosure, the seed layer includes a titanium layer and a copper layerover the titanium layer. The seed layer may be formed using, forexample, Physical Vapor Deposition (PVD). The plating may be performedusing, for example, electro-less plating.

Further referring to FIG. 1, dielectric layer 28 is formed on RDLs 26.The bottom surface of dielectric layer 28 is in contact with the topsurfaces of RDLs 26 and dielectric layer 24. In accordance with someembodiments of the present disclosure, dielectric layer 28 is formed ofa non-polymer (inorganic material), which may be silicon oxide, siliconnitride, or the like. In accordance with some embodiments of the presentdisclosure, dielectric layer 28 is formed of a polymer, which may bepolyimide, Polybenzoxazole (PBO), or the like. Dielectric layer 28 isthen patterned to form openings 30 therein. Hence, some portions of RDLs26 are exposed through the openings 30 in dielectric layer 28.

Next, referring to FIG. 2, RDLs 32 are formed to connect to RDLs 26.RDLs 32 include metal traces (metal lines) over dielectric layer 28.RDLs 32 also include vias extending into the openings in dielectriclayer 28. RDLs 32 are also formed in a plating process, wherein each ofRDLs 32 includes a seed layer (not shown) and a plated metallic materialover the seed layer. The seed layer and the plated material may beformed of the same material or different materials. RDLs 32 may includea metal or a metal alloy including aluminum, copper, tungsten, or alloysthereof. The steps for forming dielectric layers 28 and 34 and RDLs 32and 36 are represented as step 302 in the process flow 300 as shown inFIG. 39.

Referring to FIG. 3, dielectric layer 34 is formed over RDLs 32 anddielectric layer 28. Dielectric layer 34 may be formed of an inorganicmaterial, which may be selected from silicon oxide, silicon nitride,silicon carbo-nitride, silicon oxynitride, or the like.

FIG. 3 further illustrates the formation of RDLs 36, which areelectrically connected to RDLs 32. The formation of RDLs 36 may adoptthe methods and materials similar to those for forming RDLs 32. It isappreciated that although in the illustrative exemplary embodiments, twodielectric layers 28 and 34 and the respective RDLs 32 and 36 formedtherein are discussed, fewer or more dielectric layers may be adopted,depending on the routing requirement and the requirement of usingpolymers for buffering stress. For example, there may be a singledielectric layer or three, four, or more dielectric layers.

FIG. 4 illustrates the formation of passivation layers 38 and 42 andRDLs 40 and 44. The respective step is illustrated as step 304 in theprocess flow 300 as shown in FIG. 39. In accordance with someembodiments of the present disclosure, passivation layers 38 and 42 areformed of inorganic materials such as silicon oxide, silicon nitride,silicon carbo-nitride, silicon oxynitride, silicon oxy-carbo-nitride,Un-doped Silicate Glass (USG), or multiplayers thereof. Each ofpassivation layers 38 and 42 may be a single layer or a composite layer,and may be formed of a non-porous material. In accordance with someembodiments of the present disclosure, one or both of passivation layers38 and 42 is a composite layer including a silicon oxide layer (notshown separately), and a silicon nitride layer (not shown separately)over the silicon oxide layer. Passivation layers 38 and 42 have thefunction of blocking moisture and detrimental chemicals from accessingthe conductive features such as fine-pitch RDLs in the package, as willbe discussed in subsequent paragraphs.

RDLs 40 and 44 may be formed of aluminum, copper, aluminum copper,nickel, or alloys thereof. In accordance with some embodiments of thepresent disclosure, some portions of RDLs 44 are formed as metal padsthat are large enough for landing the subsequently formedThrough-Dielectric Vias (TDVs), as shown in FIG. 11. These metal padsare accordingly referred to as metal pads 44 or aluminum pads 44 inaccordance with some embodiments. Also, the number of passivation layersmay be any integer number such as one, two (as illustrated), three, ormore.

FIG. 5 illustrates the formation of one or a plurality of dielectriclayers. For example, as illustrated, dielectric layer 46 may be formedto embed the top RDLs 44 therein. Dielectric layer 48 is formed overdielectric layer 46, and may act as an etch stop layer. In accordancewith some embodiments of the present disclosure, dielectric layers 46and 48 can also be replaced with a single dielectric layer. Theavailable materials of dielectric layers 46 and 48 include siliconoxide, silicon nitride, silicon carbide, silicon oxynitride, or thelike.

FIGS. 6, 7, and 8 illustrate the formation of dielectric layers andfine-pitch RDLs in accordance with some embodiments of the presentdisclosure. The respective step is illustrated as step 306 in theprocess flow 300 as shown in FIG. 39. The formation methods may adoptthe method for forming interconnect structure for device dies based onsilicon substrates. For example, the formation methods of theinterconnect structure may include single damascene and/or dualdamascene processes. Accordingly, the resulting RDLs are alsoalternatively referred to as metal lines and vias, and the correspondingdielectric layers are alternatively referred to asInter-Metal-Dielectric (IMD) layers.

Referring to FIG. 6, vias 55, dielectric layers 50A and 54A, and etchstop layer 52A are formed. Dielectric layers 50A and 54A may be formedof silicon oxide, silicon oxynitride, silicon nitride, or the like, orlow-k dielectric materials having k values lower than about 3.0. Thelow-k dielectric materials may include Black Diamond (a registeredtrademark of Applied Materials), a carbon-containing low-k dielectricmaterial, Hydrogen SilsesQuioxane (HSQ), MethylSilsesQuioxane (MSQ), orthe like. Etch stop layer 52A is formed of a material having a highetching selectivity relative to dielectric layers 50A and 54A, and maybe formed of silicon carbide, silicon carbo-nitride, etc. In accordancewith alternative embodiments, etch stop layer 52A is not formed.

Fine-pitch RDLs 56A are formed in dielectric layers 52A and 54A forrouting. Although vias 55 and fine-pitch RDLs 56A are illustrated ashaving single damascene structures in some exemplary embodiments, vias55 and fine-pitch RDLs 56A in combination may have dual damascenestructures. It is appreciated that the single illustrated fine-pitchRDLs 56A represent a plurality of fine-pitch RDLs. Since the fine-pitchRDLs in accordance with some embodiments of the present disclosure areformed using damascene processes, it can be formed very thin withpitches (viewed from the top of the structure) smaller than, forexample, 0.8 μm. Also, since dielectric layers 34, 38, 42, 46, and 48may all be formed of inorganic materials, the pitches and the widths ofthe fine-pitch RDLs can be small. The pitches and the widths of thefine-pitch RDLs can be further reduced if dielectric layer 28 is alsoformed of inorganic material, so that there is no polymer layerunderlying the dual damascene structure. This significantly improves thedensity of the fine-pitch RDLs and the routing ability. In accordancewith some embodiments of the present disclosure in which vias 55 andfine-pitch RDLs 56A are formed using a dual damascene process, theformation process includes etching dielectric layers 48 and 50A to formvias openings, and dielectric layers 50A and 52A to form trenches,filling the via openings and the trenches with a conductive material(s),and performing a planarization such as Chemical Mechanical Polish (CMP)or mechanical grinding to remove the portions the conductive materialover dielectric layers.

In accordance with some embodiments of the present disclosure, theconductive material for forming vias 55 and fine-pitch RDLs 56A is ahomogenous material. In accordance with other embodiments of the presentdisclosure, the conductive material is a composite material including abarrier layer formed of titanium, titanium nitride, tantalum, tantalumnitride, or the like, and a copper-containing material (which may becopper or copper alloy) over the barrier layer.

FIG. 7 illustrates the formation of dielectric layers 50B and 54B andetch stop layer 52B. The materials of dielectric layers 50B and 54B maybe selected from the same candidate materials for forming dielectriclayers 50A and 54A, and the material of etch stop layer 52B may beselected from the same candidate materials for forming etch stop layer52A.

Fine-pitch RDLs 56B are also formed in dielectric layers 50B, 52B, and54B. Fine-pitch RDLs 56B include metal lines formed in dielectric layers54B and 52B and vias in dielectric layer 50B. The formation may includea dual damascene process, which includes forming trenches in dielectriclayers 54B and 52B and via openings in dielectric layer 50B, filling aconductive material(s), and then performing a planarization such asmechanical grinding or Chemical Mechanical Polish (CMP). Similarly,fine-pitch RDLs 56B may be formed of a homogenous material, or may beformed of a composite material including a barrier layer and acopper-containing material over the barrier layer.

FIG. 8 illustrates the formation of dielectric layers 50C and 54C, etchstop layer 52C, and fine-pitch RDLs 56C. The formation method and thematerials may be similar to the underlying respective layers, and henceare not repeated herein. Also, etch stop layers 52A, 52B, and 52C may beomitted in accordance with some embodiments of the present disclosure,and the corresponding etching for forming trenches may be performedusing a time-mode to control the depths of the trenches. It isappreciated that there may be more dielectric layers and layers offine-pitch RDLs formed. In addition, even if some or all of etch stoplayers 52A, 52B, and 52C may be skipped, since the dielectric layers inwhich the fine-pitch RDLs are located are formed in different processes,there may be distinguishable interfaces between the dielectric layersfor forming fine-pitch RDLs 56A, 56B, and 56C, regardless of whetherthese dielectric layers are formed of the same dielectric material ordifferent dielectric materials. In subsequent paragraphs, dielectriclayers 50A, 52A, 54A, 50B, 52B, 54B, 50C, 52C, and 54C are collectivelyand individually referred to as dielectric layers 58 for the simplicityin identification. Fine-pitch RDLs 56A, 56B, and 56C are alsocollectively and individually referred to as fine-pitch RDLs 56.

In accordance with some embodiments of the present disclosure, passivedevice 61 is formed at the same time when fine-pitch RDLs 56 are formed.Passive device 61 is thus embedded in dielectric layers 58. Passivedevice 61 may be a capacitor, an inductor, a Radio-Frequency (RF)transmission line, a transformer, or the combinations of these devices.Passive device 61 is electrically coupled to the subsequently bondeddevice dies.

Also, at the same time fine-pitch RDLs 56 are formed, stacked vias 67are also formed, with each including a plurality of dual damascenestructures (and may or may not include single damascene structures)stacked to form a connection structure penetrating through dielectriclayers 58. Stacked vias 67 in combination have similar functions as thatof Through-Dielectric Vias (TDVs) 62 as shown in FIG. 10. It isbeneficial to form stacked vias since they are formed using dualdamascene process, and hence may have widths as small as a metal line inthe dual damascene structure.

Stacked vias 67 may also be used for routing. For example, portion 56Din RDLs 56 is schematically illustrated to show that metal lines may beformed simultaneously as stacked vias 67 for routing purpose. Stackedvias 67 may thus be electrically connected sideways to other electricalcomponents. The routing metal lines may be formed in any of the metallayers of fine-pitch RDLs 56.

Referring to FIG. 9, dielectric layers 48 and 58 are etched to formThrough-Dielectric Via (TDV) openings 60. The respective step isillustrated as step 308 in the process flow 300 as shown in FIG. 39.Metal pads 44 are exposed to TDV openings 60. The top-view shapes of viaopenings 60 may be rectangles, circles, hexagons, or the like.

Next, TDV openings 60 are filled with a conductive material(s) to formTDVs 62, and the resulting structure is shown in FIG. 10. The respectivestep is illustrated as step 310 in the process flow 300 as shown in FIG.39. In accordance with some embodiments of the present disclosure, TDVs62 are formed of a homogenous conductive material, which may be a metalor a metal alloy including copper, aluminum, tungsten, or the like. Inaccordance with alternative embodiments of the present disclosure, TDVs62 have a composite structure including a conductive barrier layerformed of titanium, titanium nitride, tantalum, tantalum nitride, or thelike, and a metal-containing material over the barrier layer. Inaccordance with some embodiments of the present disclosure, a dielectricisolation layer is formed to encircle each of TDVs 62. In accordancewith alternative embodiments, no dielectric isolation layers are formedto encircle TDVs 62, and TDVs 62 are in physical contact with dielectriclayers 58. The formation of TDVs 62 also include depositing theconductive material into the TDV openings 60 (FIG. 9), and performing aplanarization to remove excess portions of the deposited material overdielectric layers 58. TDVs 62 may have greater widths than stacked vias67 due to the difficulty in forming deep openings 60 (FIG. 9)penetrating through the plurality of dielectric layers 58 and 48, whichhave different etching properties. The resistance of TDVs 62 is low.Accordingly, TDVs 62 may be used for conducting power while the areaoccupied by TDVs 62 is not significant due to the small number of TDVs62. Combining stacked vias 67 and TDVs 62 may increase the number ofsignal connections (using stacked vias 67), while can still servelow-loss power transmission using wide TDVs 62. In accordance with someembodiments, TDVs 62 are not formed.

FIG. 11 illustrates the formation of bond pads 66 and dielectric layer64, and bond pads 66 are located in dielectric layer 64. The respectivestep is illustrated as step 312 in the process flow 300 as shown in FIG.39. Bond pads 66 may be formed of a metal that is easy for forminghybrid bonding. In accordance with some embodiments of the presentdisclosure, bond pads 66 are formed of copper or a copper alloy.Dielectric layer 64 may be formed of silicon oxide, for example. The topsurfaces of bond pads 66 and dielectric layer 64 are coplanar. Theplanarity may be achieved, for example, through a planarization stepsuch as a CMP or a mechanical grinding step.

In accordance with some embodiments of the present disclosure, bond pads66 and dielectric layer 64 are not formed. Accordingly, device dies 68Aand 68B are bonded to the top RDLs 56 (shown as 56C in FIG. 8) andpossibly dielectric layer 54C (FIG. 8) directly.

Throughout the description, the components over layer 22 (or siliconwafer 23) are in combination referred to as interposer 100. Interposer100, different from conventional interposers that were formed based onsilicon substrates, are formed based on dielectric layers 58. No siliconsubstrate is in interposer 100, and hence interposer 100 is referred toas a silicon-substrate-free interposer or a Si-less interposer. Stackedvias 67 and TDVs 62 are formed in dielectric layers 58 to replaceconventional through-silicon vias. Since silicon substrates aresemiconductive, it may adversely affect the performance of the circuitsand the connections formed therein and thereon. For example, signaldegradation may be caused by the silicon substrate, and such degradationmay be avoided in the embodiments of the present disclosure since theTDVs 62 and stacked vias 67 are formed in dielectric layers.

Next, first-layer device dies 68A and 68B are bonded to interposer 100,as shown in FIG. 12. The respective step is illustrated as step 314 inthe process flow 300 as shown in FIG. 39. In accordance with someembodiments of the present disclosure, device dies 68A and 68B include alogic die, which may be a Central Processing Unit (CPU) die, a MicroControl Unit (MCU) die, an input-output (IO) die, a BaseBand (BB) die,or an Application processor (AP) die. Device dies 68A and 68B may alsoinclude a memory die. Device dies 68A and 68B include semiconductorsubstrates 70A and 70B, respectively, which may be silicon substrates.Through-Silicon Vias (TSVs) 71A and 71B, sometimes referred to asthrough-semiconductor vias or through-vias, are formed to penetratethrough semiconductor substrates 70A and 70B, respectively, and are usedto connect the devices and metal lines formed on the front side (theillustrated bottom side) of semiconductor substrates 70A and 70B to thebackside. Also, device dies 68A and 68B include interconnect structures72A and 72B, respectively, for connecting to the active devices andpassive devices in device dies 68A and 68B. Interconnect structures 72Aand 72B include metal lines and vias (not shown).

Device die 68A includes bond pads 74A and dielectric layer 76A at theillustrated bottom surface of device die 68A. The illustrated bottomsurfaces of bond pads 74A are coplanar with the illustrated bottomsurface of dielectric layer 76A. Device die 68B includes bond pads 74Band dielectric layer 76B at the illustrated bottom surface. Theillustrated bottom surfaces of bond pads 74B are coplanar with theillustrated bottom surface of dielectric layer 76B.

The bonding may be achieved through hybrid bonding. For example, bondpads 74A and 74B are bonded to bond pads 66 through metal-to-metaldirect bonding. In accordance with some embodiments of the presentdisclosure, the metal-to-metal direct bonding is copper-to-copper directbonding. Furthermore, dielectric layers 76A and 76B are bonded todielectric layer 64, for example, with Si—O—Si bonds generated. Thehybrid bonding may include a pre-bonding and an anneal, so that themetals in bond pads 74A (and 74B) inter-diffuse with the metals in therespective underlying bond pads 66.

Fine-pitch RDLs 56 electrically interconnect bond pads 74A and bond pads74B, and are used for the signal communication between device dies 68Aand 68B. Fine-pitch RDLs 56 have small pitches and small widths.Accordingly, the density of fine-pitch RDLs 56 is high, and hence enoughcommunication channels may be formed for the direct communicationbetween device dies 68A and 68B. On the other hand, TDVs 62 and stackedvias 67 provide direct connection from device dies 68A and 68B to thecomponent (which may be a package substrate, a Printed Circuit Board(PCB), or the like) that will be bonded to interposer 100. Furthermore,the bonding between bond pads 74A/74B and 66 are through bond padsrather than through solder joints, which are typically much larger thanthe bond pads. Accordingly, the horizontal sizes of the bonds are small,and more bonds can be implemented to provide enough communicationchannels.

Further referring to FIG. 12, a backside grinding is performed to thindevice dies 68A and 68B, for example, to a thickness between about 15 μmand about 30 μm. The respective step is illustrated as step 316 in theprocess flow 300 as shown in FIG. 39. Through the thinning, the aspectratio of gaps 78 between neighboring device dies 68A and 68B is reducedin order to perform gap filling. Otherwise, the gap filling is difficultdue to the otherwise high aspect ratio of openings 78. After thebackside grinding, TSVs 71A and 71B may be revealed. Alternatively, TSVs71A and 71B are not revealed at this time. Instead, TSVs 71A and 71B maybe revealed in the step shown in FIG. 17.

Next, gaps 78 are filled by gap-filling material 80, as shown in FIG.13. The respective step is illustrated as step 318 in the process flow300 as shown in FIG. 39. In accordance with some embodiments of thepresent disclosure, gap-filling material 80 includes an oxide such assilicon oxide, which may be formed using tetraethyl orthosilicate(TEOS). The formation method may include Chemical Vapor Deposition(CVD), High-Density Plasma Chemical Vapor Deposition (HDPCVD), or thelike. In accordance with alternative embodiments, gap-filling material80 is formed of a polymer such as PBO, polyimide, or the like. Aplanarization step is then performed to remove excess portions ofgap-filling material 80, so that substrates 70A and 70B of device dies68A and 68B are revealed. The resulting structure is shown in FIG. 14.

FIG. 15 illustrates the formation of TDVs 162, which are formed byetching-through gap-filling material 80 in an anisotropic etching stepto form via openings, and filling the respective openings with aconductive material(s). The respective step is illustrated as step 320in the process flow 300 as shown in FIG. 39. Some bond pads 66 areexposed to the via openings, wherein the etching may be performed usingbond pads 66 as etch stop layers. TDVs 162 may have a structure similarto the structure of TDVs 62, and may include barrier layers and ametallic material over the barrier layers. The materials of TDVs 162 mayalso be selected from the similar candidate materials for forming TDVs62.

Referring to FIG. 16, substrates 70A and 70B are recessed to formrecesses 73, and the top ends of TSVs 71A and 71B protrude slightlyabove the top surfaces of substrates 70A and 70B, respectively. Therespective step is illustrated as step 322 in the process flow 300 asshown in FIG. 39. Recesses 73 are then filled with a dielectric materialsuch as silicon oxide to form dielectric layers 75A and 75B, and theresulting structure is shown in FIG. 17. The respective step isillustrated as step 324 in the process flow 300 as shown in FIG. 39. Theformation process includes a deposition process to deposit a blanketdielectric layer, and preforming a planarization to remove portions ofthe blanket dielectric layer higher than the top ends of TSVs 71A and71B.

Next, second-layer device dies 168A and 168B are bonded to device dies68A and 68B, as shown in FIG. 18. The respective step is illustrated asstep 326 in the process flow 300 as shown in FIG. 39. In accordance withsome embodiments of the present disclosure, device dies 168A and 168Binclude logic dies, memory dies, or combinations thereof. Device dies168A and 168B include semiconductor substrates 170A and 170B,respectively, which may be semiconductor substrates such as siliconsubstrates. TSVs (not shown) may be formed in semiconductor substrates170A and 170B if there are third-layer device dies bonded over devicedies 168A and 168B. Alternatively, TSVs are not formed in semiconductorsubstrates 170A and 170B. Also, device dies 168A and 168B includeinterconnect structures 172A and 172B, respectively, for connecting tothe active devices and passive devices in device dies 168A and 168B.Interconnect structures 172A and 172B include metal lines and vias (notshown).

Device die 168A includes bond pads 174A and dielectric layer 176A at theillustrated bottom surface of device die 168A. The illustrated bottomsurfaces of bond pads 174A are coplanar with the illustrated bottomsurface of dielectric layer 176A. Device die 168B includes bond pads174B and dielectric layer 176B at the illustrated bottom surface. Theillustrated bottom surfaces of bond pads 174B are coplanar with theillustrated bottom surface of dielectric layer 176B.

The bonding may be achieved through hybrid bonding. For example, bondpads 174A and 174B are directly bonded to TSVs 71A and 71B throughmetal-to-metal direct bonding. In accordance with some embodiments ofthe present disclosure, the metal-to-metal direct bonding iscopper-to-copper direct bonding. Furthermore, dielectric layers 176A and176B are bonded to dielectric layers 75A and 75B, for example, withSi—O—Si bonds generated. Depending on the material of gap-fillingmaterial 80, dielectric layers 176A and 176B may be bonded togap-filling material 80, or may be in contact with, but not bonded to(no bonds are formed), gap-filling material 80.

Next, device dies 168A and 168B may be thinned, similar to the thinningof device dies 68A and 68B. The gaps between neighboring device dies168A and 168B are then filled by gap-filling material 180, as shown inFIG. 19. The respective step is illustrated as step 328 in the processflow 300 as shown in FIG. 39. In accordance with some embodiments of thepresent disclosure, gap-filling material 180 is formed using a methodselected from the same candidate methods for forming gap-fillingmaterial 80. Gap-filling material 180 may include an oxide such assilicon oxide, silicon nitride, PBO, polyimide, or the like. Aplanarization step is then performed to remove excess portions ofgap-filling material 180, so that substrates 170A and 170B of devicedies 168A and 168B are revealed.

Dielectric layer 182 is then deposited as a blanket layer, for example,using CVD, PECVD, ALD, or the like. The resulting structure is alsoshown in FIG. 19. The respective step is illustrated as step 330 in theprocess flow 300 as shown in FIG. 39. In accordance with someembodiments of the present disclosure, dielectric layer 182 is formed ofan oxide such as silicon oxide, silicon oxynitride, or the like.

Next, referring to FIG. 20, trenches 184 are formed by etchingdielectric layer 182 and substrates 170A and 170B, so that trenches 184extend into dielectric layer 182 and substrates 170A and 170B. Depth D1of the portions of trenches 184 inside substrates 170A and 170B may begreater than about 1 μm, and may be between about 2 μm and about 5 μm,depending on the thickness T1 of substrates 170A and 170B. For example,depth D1 may be between about 20 percent and about 60 percent ofthickness T1. It is appreciated that the values recited throughout thedescription are examples, and may be changed to different values.

Trenches 184 may be distributed in various patterns. For example,trenches 184 may be formed as discrete openings, which may be allocatedto have a pattern of an array, a pattern of beehive, or other repeatpatterns. The top-view shapes of trenches 184 may be rectangles,circles, hexagons, or the like. In accordance with alternativeembodiments, trenches 184, when viewed in the top view of the structureshown in FIG. 20, may be parallel trenches that have lengthwisedirections in a single direction. Trenches 84 may also be interconnectedto form a grid. The grid may include a first plurality of trenchesparallel to each other and evenly or unevenly spaced, and a secondplurality of trenches parallel to each other and evenly or unevenlyspaced. The first plurality of trenches and the second plurality oftrenches intercept with each other to form the grid, and the firstplurality of trenches and the second plurality of trenches may or maynot be perpendicular to each other in the top view.

Trenches 184 are then filled to form bond pads 187, as shown in FIG. 21.The respective step is also illustrated as step 332 in the process flow300 as shown in FIG. 39. It is appreciated that although features 187are referred to as bond pads, features 187 may be discrete pads,interconnected metal lines, or a metal grid. In accordance with someembodiments of the present disclosure, bond pads 187 are formed ofcopper or other metals suitable for hybrid bonding (due to relativelyeasiness in diffusing). After the filling, a planarization is performedto planarize the top surfaces of bond pads 187 with the top surface ofdielectric layer 182. The planarization may include a CMP or amechanical grinding.

Next, as shown in FIG. 22, blank die 88 is bonded to device dies 168Aand 168B. The respective step is illustrated as step 332 in the processflow 300 as shown in FIG. 39. Blank die 88 includes bulk substrate 194,which may be a silicon substrate or a metal substrate. When formed ofmetal, substrate 194 may be formed of copper, aluminum, stainless steel,or the like. When substrate 194 is formed of silicon, there is no activedevice and passive device formed in blank die 88. Blank die 88 includestwo functions. First, blank die 88 provides mechanical support to theunderlying structure since device dies 68A, 68B, 168A, and 168B havebeen thinned in order to allow for better gap filling. Also, silicon ormetal (of substrate 194) has a high thermal conductivity, and henceblank die 88 may act as a heat spreader. Since the formation of thestructure in FIG. 22 is at wafer-level, a plurality of blank diesidentical to the illustrated blank dies 88 are also bonded to therespective underlying device dies that are identical to device dies 168Aand 168B.

Dielectric layer 190 is formed at the surface of substrate 194.Dielectric layer 190 may be formed of silicon oxide or siliconoxynitride, for example. Also, bond pads 192 are formed in dielectriclayer 190, and the illustrated bottom surfaces of bond pads 192 arecoplanar with the illustrated bottom surface of dielectric layer 190.The pattern and the horizontal sizes of bond pads 192 may be the same asor similar to that of the respective bond pads 187, so that bond pads192 and bond pads 187 may be bonded to each other with a one-to-onecorrespondence.

The bonding of blank die 88 onto device dies 168A and 168B may beachieved through hybrid bonding. For example, dielectric layers 182 and190 are bonded to each other, and may form Si—O—Si bonds. Bond pads 192are bonded to the respective bond pads 187 through metal-to-metal directbonding.

Advantageously, bond pads 187, by contacting (and even being insertedinto) substrates 170A and 170B, provide a good thermal dissipating path,so that the heat generated in device dies 68A, 68B, 168A and 168B caneasily dissipate into bulk substrate 194, and hence bulk substrate 194is used as a heat spreader.

Referring to FIG. 23, photo resist 183 is applied and patterned.Dielectric layer 182 and gap-filing material 180 are then etched usingthe patterned photo resist 183 as an etching mask to reveal someportions of interposer 100. The respective step is illustrated as step334 in the process flow 300 as shown in FIG. 39. In accordance with someembodiments of the present disclosure, some device dies such as devicedie 68B are revealed. Some of TSVs 71B and TDVs 162 may also be exposed.

FIG. 24 illustrates the bonding of die stack 212 onto the first-layerstructure. The respective step is illustrated as step 336 in the processflow 300 as shown in FIG. 39. Die stack 212 may be bonded to TDVs 162,device dies (such as die 68B), or both TDVs 162 and the device dies. Diestack 212 may be a memory stack including a plurality of stacked dies214, wherein TSVs (not shown) may be formed in dies 214 to performinterconnection. Die stack 212 may also be a High Bandwidth Memory (HBM)cube. In accordance with some embodiments of the present disclosure, diestack 212 is bonded to the underlying structure through hybrid bonding,wherein electrical connectors 216 (bond pads in some embodiments) in diestack 212 are bonded to TDVs 162 and TSVs 71B through metal-to-metaldirect bonding, and dielectric layer 218 of die stack 212 is bonded togap-filling material 80 (an oxide, for example) and dielectric layer 75Bthrough oxide-to-oxide bonding (or fusion bonding). In accordance withalternative embodiments, electrical connectors 216 are solder regions,and the bonding is solder bonding. In accordance with yet alternativeembodiments, electrical connectors 216 are micro-bumps protruding beyondthe surface dielectric layer 218 of die stack 212. Micro-bumps 216 maybe bonded to TDVs 162 and TSVs 71B through metal-to-metal direct bondingor solder bonding, and no oxide-to-oxide bonding occurs between diestack 212 and gap filling material 80 and dielectric layer 75B.

Next, gap-filling material 220 (FIG. 25) is filled into the gaps betweenblank die 88 and die stack 212. Gap-filling material 220 may be formedof an oxide such as silicon oxide or a polymer such as PBO or polyimide.In accordance with some embodiments in which carrier 20 (rather thansilicon wafer 23) is used, the structure formed on carrier 20 isde-bonded from carrier 20, for example, by projecting light such as UVlight or laser on release layer 22 to decompose release layer 22. Theresulting structure is shown in FIG. 26. Carrier 20 and release layer 22are removed from the overlying structure, which is referred to ascomposite wafer 102 (FIG. 26). The respective step is illustrated asstep 338 in the process flow 300 as shown in FIG. 39. In accordance withsome embodiments of the present disclosure in which silicon wafer 23(rather than carrier wafer 20, FIG. 24) is used, silicon wafer 23 may beremoved by mechanical grinding, CMP, or a dry etching. If needed, acarrier swap may be performed to attach another carrier 222 over theillustrated structure before carrier 20 (or silicon wafer 23) isremoved, and the new carrier 222 is used to provide mechanical supportduring the formation of electrical connectors in the subsequent step.

FIG. 26 also illustrates the formation of electrical connectors 110,which may penetrate through dielectric layer 24, and connect to RDLs 26.In accordance with some embodiments, a polymer layer(s) (not shown) isformed on dielectric layer 24, and electrical connectors 110 may alsoextend into the polymer layer. Electrical connectors 110 may be metalbumps, solder bumps, metal pillars, wire bonds, or other applicableconnectors. A die-saw step is performed on composite wafer 102 toseparate composite wafer 102 into a plurality of packages 104. Therespective step is also illustrated as step 340 in the process flow 300as shown in FIG. 39. Packages 104 are identical to each other, and eachof packages 104 may include two layers of device dies and die stack 212.The resulting package 104 is shown in FIG. 27A.

FIGS. 27B, 27C, 27D, and 27E and FIGS. 28 through 35 illustrate thecross-sectional views of packages and the intermediate stages in theformation of the packages in accordance with some embodiments of thepresent disclosure. Unless specified otherwise, the materials and theformation methods of the components in these embodiments are essentiallythe same as the like components, which are denoted by like referencenumerals in the embodiments shown in FIGS. 1 through 27A. The detailsregarding the formation process and the materials of the componentsshown in FIGS. 27B, 27C, 27D, and 27E and FIGS. 28 through 35 may thusbe found in the discussion of the embodiment shown in FIGS. 1 through27A.

FIG. 27B illustrates the package formed in accordance with someembodiments of the present disclosure. These embodiments are similar tothe embodiments shown in FIG. 27A, except that bond pads 187 and 192 anddielectric layer 190 (as in FIG. 27A) are not formed. Bulk substrate194, which may be a blank silicon die, is bonded to dielectric layer 82through fusion bonding.

In accordance with alternative embodiments of the present disclosure,bulk substrate 194 is a blank metal substrate. Accordingly, layer 182 inFIG. 27B may be formed of a Thermal Interface Material (TIM), which isan adhesive having a high thermal conductivity, for example, higher thanabout 1 W/k*m or higher than bout 5 W/k*m.

FIG. 27C illustrates the package 104 formed in accordance with someembodiments of the present disclosure. These embodiments are similar tothe embodiments shown in FIG. 27A, except that device dies havingdifferent thicknesses may be placed at a same level. For example, devicedie 68B is thicker than device die 68A. Accordingly, device die 68Binclude portions extending to the same levels as device dies 68A and168A. It is appreciated that although blank substrate 194 is illustratedas bonding to device dies 168A and 68B through fusion bonding or throughan oxide/TIM 182, the same bonding structure shown in FIG. 27A, whichincludes bond pads 187 and bond pads 192, may be used. In accordancewith some embodiments, die stack 212 has a portion level with a portionof the blank die 88.

FIG. 27D illustrates the package 104 formed in accordance with someembodiments of the present disclosure. These embodiments are similar tothe embodiments shown in FIG. 27C, except that no blank die 88 (as shownin FIG. 27C) is used. Die stack 212, instead of placed over gap fillingmaterial 80, extends into gap filling material 80.

FIG. 27E illustrates the package 104 formed in accordance with someembodiments of the present disclosure. These embodiments are similar tothe embodiments shown in FIG. 27A, except that die stack 212, instead ofextending into encapsulating material 180, is located over encapsulatingmaterial 180. Through-vias 262 are formed in encapsulating material 180to electrically couple to the underlying through vias 162 and stackedvias 67.

FIGS. 28 through 32 illustrate the cross-sectional view of intermediatestages in the formation of a package in accordance with some embodimentsof the present disclosure. The respective package includes a singlelayer of device dies. The initial steps are similar to the steps shownin FIGS. 1 through 17. The resulting structure is also shown in FIG. 17.Next, referring to FIG. 28, dielectric layer 182 and bond pads 187 mayor may not be formed, and bond pads 187 are illustrated as dashed.

Next, as shown in FIG. 29, blank die 88 is bonded, either through hybridbonding, fusion bonding, or adhesion through TIM. FIG. 30 illustratesthe bonding of die stack 212. In FIG. 31, blank die 88 and die stack 212are encapsulated in gap-filling material 220. A planarization may beperformed to expose blank die 88. In subsequent steps, interposer 100and the overlying structure are de-bonded from carrier 20. FIG. 32illustrates the formation of electrical connectors 110. A die-saw isthen performed to form package 104.

FIGS. 33 through 35 illustrate the cross-sectional view of intermediatestages in the formation of a package in accordance with some embodimentsof the present disclosure. The respective package and the formationprocess of the structure shown in FIG. 33 are similar to what are shownin FIGS. 28 through 32, except TDVs 162 and their connecting conductivefeatures including some of the stacked vias 67, TDVs 62, and RDLs 32,36, and 44 are not formed. The bonding of die stack 212 to theunderlying structure, for example, gap-filling material 80, is throughfusion bonding. Accordingly, the bond pads 216 of stacked dies 212 arein contact with gap-filling material 80 or a dielectric layer formedthereon.

FIG. 33 includes some metal pads 44B, which are connected to RDLs 44A.Metal pads 44B and RDLs 44A are parts of RDLs 44. Metal pads 44B mayform a hollow ring. FIG. 38 illustrates some exemplary metal pads 44Band the connecting RDLs 44A. Metal pads 44B are formed as rings, withthe openings 45 inside the rings filled by dielectric layer 46 (FIG.33). It is appreciated that although the metal pads 44B are illustratedas being parts of RDLs 44, the similar metal pads may be formed in anyof the layers in interposer 100. Metal pads 44B are thus electricallyconnected to other conductive features in interposer 100.

Next, referring to FIG. 34, deep TDVs 162 are formed from the bottomside of interposer 100. The formation process includes etching thedielectric layers to form openings, and then filling the openings withconductive materials. The formation process and the materials aresimilar to the formation of TDVs 62. In the formation of the openings,metal pads 44B are used as etch stop layers, so that the upper portionsof the openings are defined by the size and the shape of openings 45(FIG. 38). The opening is further stopped by metal pads 216 in die stack212. The formation of TDVs 162 is thus self-aligned by metal pads 44B.Metal pads 44B and RDLs 44A in combination electrically connect devicedies 68A and 68B to die stacks 212 through TDVs 162. Electricalconnectors 110 are then formed, and package 104 is resulted after thedie-saw, as shown in FIG. 35.

FIG. 36 illustrates a package 112 in which package 104 (refer to FIGS.27A, 27B. 27C, 27D, 27E, 32, and 35) is embedded. The package includesmemory cubes 114, which includes a plurality of stacked memory dies (notshown separately). Package 104 and memory cubes 114 are encapsulated inencapsulating material 118, which may be a molding compound. Dielectriclayers and RDLs (collectively illustrated as 116) are underlying andconnected to package 104 and memory cubes 114. In accordance with someembodiments of the present disclosure, dielectric layers and RDLs 116are formed using similar materials and have similar structures as thatare shown in FIGS. 1 through 11.

FIG. 37 illustrates Package-on-Package (PoP) structure 132, which hasIntegrated Fan-Out (InFO) package 138 bonded with top package 140. InFOpackage 138 also includes package 104 embedded therein. Package 104 andthrough-vias 134 are encapsulated in encapsulating material 130, whichmay be a molding compound. Package 104 is bonded to dielectric layersand RDLs, which are collectively referred to as 146. Dielectric layersand RDLs 146 may also be formed using similar materials and have similarstructures as what are shown in FIGS. 1 through 11.

The embodiments of the present disclosure have some advantageousfeatures. By forming the fine-pitch RDLs in interposers using theprocesses typically used on silicon wafers (such as damasceneprocesses), the fine-pitch RDLs may be formed to be thin enough toprovide the capability for the communication of two or more device diesall through the fine-pitch RDLs. Stacked vias are formed to replace someof the TDVs, so that the chip-area occupation is reduced. Self-alignedTDVs are formed to connect to die stack, wherein the metal pads used foraligning the TDVs are also used for connecting the self-aligned TDVs toother features and device dies in the package. Also, passive devices mayalso be formed when the fine-pitch RDLs are formed.

In accordance with some embodiments, a method includes forming aplurality of dielectric layers; forming a plurality of redistributionlines in the plurality of dielectric layers; when the plurality ofredistribution lines is formed, simultaneously forming stacked vias inthe plurality of dielectric layers, wherein the stacked vias form acontinuous electrical connection penetrating through the plurality ofdielectric layers; forming a dielectric layer over the stacked vias andthe plurality of dielectric layers; forming a plurality of bond pads inthe dielectric layer; and bonding a first device die to the dielectriclayer and a first portion of the plurality of bond pads through hybridbonding. In an embodiment, the method includes bonding a second devicedie to the dielectric layer and a second portion of the plurality ofbond pads through hybrid bonding, wherein the plurality ofredistribution lines connects the first device die to the second devicedie. In an embodiment, the forming the plurality of redistribution linescomprises damascene processes. In an embodiment, the method includesetching the plurality of dielectric layers to form an opening; andfilling the opening to form a through-dielectric via penetrating throughthe plurality of dielectric layers. In an embodiment, the methodincludes bonding an additional device die to the first device die,wherein the additional device die is bonded directly to through-siliconvias in the first device die; forming an oxide layer over and contactinga semiconductor substrate of the additional device die; forming a bondpad extending into the oxide layer; and bonding a blank die to the oxidelayer and the bond pad through hybrid bonding. In an embodiment, theplurality of dielectric layers is formed over a glass carrier; and themethod further includes de-bonding the glass carrier; and after theglass carrier is de-bonded, forming a self-aligned through-dielectricvia to penetrate through the plurality of dielectric layers, wherein theself-aligned through-dielectric via is stopped on a bond pad of a diestack. In an embodiment, the plurality of dielectric layers is formedover a silicon wafer, and the method further comprises grinding,polishing, or etching the silicon wafer from the plurality of dielectriclayers.

In accordance with some embodiments, a method includes forming aplurality of dielectric layers; forming a plurality of redistributionlines in each of the plurality of dielectric layers; forming a passivedevice in the plurality of dielectric layers; forming a firstthrough-dielectric via and a second through-dielectric via penetratingthrough the plurality of dielectric layers; forming a dielectric layerover the plurality of dielectric layers; forming a plurality of bondpads in the dielectric layer and electrically coupling to the firstthrough-dielectric via, the second through-dielectric via, and theplurality of redistribution lines; and bonding a first device die and asecond device die to the dielectric layer and the plurality of bond padsthrough hybrid bonding, wherein the first device die and the seconddevice die are electrically interconnected through the plurality ofredistribution lines, and the first device die and the second device dieare connected to the first through-dielectric via and the secondthrough-dielectric via, respectively. In an embodiment, the plurality ofredistribution lines is formed using damascene processes. In anembodiment, the method includes filling a gap-filling material onopposite sides the first device die and the second device die; forming athird through-dielectric via penetrating through the gap-fillingmaterial; and bonding a die stack to the third through-dielectric via.In an embodiment, the plurality of dielectric layers is formed over asilicon wafer, and the method further comprises removing the siliconwafer from the plurality of dielectric layers. In an embodiment, theforming the first through-dielectric via and the secondthrough-dielectric via comprises etching the plurality of dielectriclayers to form a first opening and a second opening; and filling thefirst opening and the second opening with a conductive material. In anembodiment, the method includes, when the plurality of redistributionlines is formed, simultaneously forming stacked vias in the plurality ofdielectric layers, wherein the stacked vias form a continuous electricalconnection penetrating through the plurality of dielectric layers. In anembodiment, the method includes bonding a third device die on top of thefirst device die; forming a dielectric layer over the third device die;and bonding a blank die to the dielectric layer.

In accordance with some embodiments, a package includes a plurality ofdielectric layers; a plurality of redistribution lines in each of theplurality of dielectric layers; a through-dielectric via penetratingthrough the plurality of dielectric layers, wherein thethrough-dielectric via has a substantially straight edge penetratingthrough the plurality of dielectric layers; stacked vias in theplurality of dielectric layers, wherein the stacked vias areelectrically connected to each other to form a continuous electricalconnection penetrating through the plurality of dielectric layers; aplurality of bond pads over and connected to the through-dielectric viaand the plurality of redistribution lines; a first dielectric layer,with the plurality of bond pads located in the first dielectric layer;and a first device die bonded to the first dielectric layer and a firstportion of the plurality of bond pads through hybrid bonding. In anembodiment, the package further includes a second device die bonded tothe first dielectric layer and a second portion of the plurality of bondpads through hybrid bonding, wherein the first device die and the seconddevice die are electrically coupled to each other through the pluralityof redistribution lines. In an embodiment, the package further includesa second device die over and bonded to the first device die; a bond padcontacting a semiconductor substrate of the second device die, whereinat least a portion of the bond pad is over the semiconductor substrateof the second device die; a second dielectric layer, with the bond padhaving at least a portion in the second dielectric layer; and a bulksubstrate over and bonded to the second dielectric layer and the bondpad. In an embodiment, the bulk substrate is formed of silicon, and noactive device and passive device is formed on the bulk substrate. In anembodiment, the bond pad further extends into the semiconductorsubstrate of the second device die. In an embodiment, the bond pad formsa grid.

In accordance with some embodiments, a method includes forming aplurality of dielectric layers over a silicon wafer; forming a pluralityof redistribution lines in the plurality of dielectric layers; when theplurality of redistribution lines is formed, simultaneously formingstacked vias in the plurality of dielectric layers, wherein the stackedvias form a continuous electrical connection penetrating through theplurality of dielectric layers; forming a dielectric layer over thestacked vias and the plurality of dielectric layers; forming a pluralityof bond pads in the dielectric layer; bonding a first device die to thedielectric layer and a first portion of the plurality of bond padsthrough hybrid bonding; removing the silicon wafer from the plurality ofdielectric layers; and forming electrical connections electricallycoupling to the plurality of redistribution lines. In an embodiment, theremoving the silicon wafer comprises performing a mechanical grinding onthe silicon wafer. In an embodiment, the removing the silicon wafercomprises performing a chemical mechanical polish on the silicon wafer.In an embodiment, the removing the silicon wafer comprises performing adry etching on the silicon wafer. In an embodiment, the method includesforming a passive device in the plurality of dielectric layers. In anembodiment, the method includes encapsulating the first device die in agap-filling material; and after the silicon wafer is removed, forming athrough-dielectric via penetrating through the plurality of dielectriclayers and the gap-filling material.

In accordance with some embodiments, a package includes a plurality ofdielectric layers; stacked vias penetrating through the plurality ofdielectric layers, wherein the stacked vias have dual damascenestructures, and the stacked vias are interconnected to form a continuouselectrical connection structure; a device die over the plurality ofdielectric layers, wherein the device die is bonded to underlyingstructures through hybrid bonding, and the device die is electricallycoupled to the stacked vias; and a die stack over and bonded to thedevice die. In an embodiment, the die stack is bonded to the device diethrough hybrid bonding.

In accordance with some embodiments, a package includes a plurality ofdielectric layers; a passive device in the plurality of dielectriclayers; a through-dielectric via penetrating through the plurality ofdielectric layers; a first device die over and electrically coupling tothe through-dielectric via, wherein the first device die comprises asemiconductor substrate; a dielectric layer over the first device die; abond pad in the dielectric layer, wherein the bond pad penetrate throughthe dielectric layer and further extends into the semiconductorsubstrate of the first device die; and a die stack over and bonded tothe first device die. In an embodiment, the package further includes asecond device die between the first device die and thethrough-dielectric via.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package comprising: a blank die comprising asubstrate; a first dielectric material encapsulating a first die, thefirst die comprising a blank substrate free of passive devices andactive devices, wherein the first die is bonded to the blank die throughan adhesive layer that has a thermal conductivity higher than 5 W/K*m;and a second die bonded to the first die, the second die encapsulated bya second dielectric material.
 2. The package of claim 1, wherein thesubstrate comprises a metal.
 3. The package of claim 1, wherein theblank die is free of passive devices and active devices and thesubstrate comprises silicon.
 4. The package of claim 1, wherein a firstbond pad of the first die is directly bonded to a through-silicon via(TSV) of the second die through metal-to-metal direct bonding.
 5. Thepackage of claim 1, wherein a first dielectric layer of the first die isdirectly bonded to a second dielectric layer of the second die throughdielectric-to-dielectric bonding.
 6. The package of claim 5, wherein thefirst dielectric layer of the first die is further directly bonded tothe second dielectric material encapsulating the second die.
 7. Thepackage of claim 1, further comprising a plurality of stacked dies inthe first dielectric material and a third dielectric material, wherein atop surface of the plurality of stacked dies and a top surface of theblank die are level.
 8. The package of claim 7, wherein a second bondpad of the plurality of stacked dies is bonded to a through-dielectricvia (TDV) in the second dielectric material through metal-to-metaldirect bonding and a third dielectric layer of the plurality of stackeddies is bonded to the second dielectric material throughdielectric-to-dielectric bonding.
 9. A package comprising: a first diebonded to a second die, wherein the first die and the second die areencapsulated by a first dielectric material; a third die encapsulated bythe first dielectric material; a plurality of stacked dies in the firstdielectric material and a second dielectric material, wherein bottomsurfaces of the second die, the third die, and the plurality of stackeddies are at a same level; and a blank die bonded to a first substrate ofthe first die and a second substrate of the third die.
 10. The packageof claim 9, wherein the blank die is bonded to the first substrate ofthe first die and the second substrate of the third die through anadhesive layer that has a thermal conductivity higher than 5 W/K*m. 11.The package of claim 9, wherein the third die is thicker than the seconddie.
 12. The package of claim 9, further comprising: a plurality ofdielectric layers; and a first dielectric layer over the plurality ofdielectric layers, wherein the first dielectric layer is bonded to asecond dielectric layer of the second die, a third dielectric layer ofthe third die and a fourth dielectric layer of the plurality of stackeddies through dielectric-to-dielectric bonds.
 13. The package of claim12, further comprising: a plurality of through-dielectric vias (TDVs)extending through the plurality of dielectric layers; and a plurality ofstacked vias in the plurality of dielectric layers.
 14. The package ofclaim 13, wherein the second die is directly bonded to a first TDV ofthe plurality of TDVs and a first stacked via of the plurality ofstacked vias, and the third die is directly bonded to a second TDV ofthe plurality of TDVs and a second stacked via of the plurality ofstacked vias.
 15. The package of claim 14, wherein the plurality ofstacked dies is bonded to a third TDV of the plurality of TDVs and athird stacked via of the plurality of stacked vias throughmetal-to-metal direct bonding.
 16. The package of claim 14, whereinelectrical connectors of the plurality of stacked dies are bonded to athird TDV of the plurality of TDVs and a third stacked via of theplurality of stacked vias through solder bonding.
 17. A packagecomprising: an interconnect structure; a first plurality of dielectriclayers over the interconnect structure; a first through-dielectric via(TDV), a second TDV, a first stacked via, and a second stacked viaextending through the first plurality of dielectric layers, wherein thefirst TDV, the second TDV, the first stacked via, and the second stackedvia are electrically connected to the interconnect structure; a firstdie bonded to the first TDV and the first stacked via; and a die stackbonded to the second TDV and the second stacked via.
 18. The package ofclaim 17, wherein the first die is bonded to the first TDV and the firststacked via through metal-to metal direct bonding.
 19. The package ofclaim 17, wherein the die stack is bonded to the second TDV and thesecond stacked via through metal-to metal direct bonding.
 20. Thepackage of claim 17, wherein electrical connectors of the die stack arebonded to the second TDV and the second stacked via through solderbonding.